<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>13_圆角边框</title>
<style>
    .box1{
        width: 800px;
        height: 800px;
        border: 1px solid black;
        margin: 0 auto;
        /*border-radius: 200px 150px 100px 50px ;!*左上,右上,右下,左下*!*/
        /*border-radius: 200px ;*/
        border-radius: 45%;
    }
</style>
</head>
<body>
<div class="box1"></div>
</body>
</html>